Short term weather predictions (e.g., 30-120 minutes) of the location of storms are extremely important to many sectors of the population. For example, aviation systems, traffic information systems, power companies and commuters realize important safety and economic benefits from accurate predictions of organized storms. Unfortunately, the classic weather problem of determining the motion of organized storms has not led to accurate automated forecasts for the short term time scale.
Organized storms are large scale meteorological events, often resulting from frontal discontinuities or cyclonic disturbances. Organized storms include clusters or groups of cells which occur alone or in larger line storms, hurricanes, tropical storms or in association with low pressure centers. Large single cells, including hailstorms, tornadic cells, and supercells, are also considered organized storms due to their longer lifetime and broader geographic range. Conversely, airmass storms are small scale, unorganized convective elements of limited duration and geographic range. Any convective element (i.e., cell) can be categorized as part of an organized storm or an individual airmass storm.
The storm tracking community has attempted for years to determine not only storm advection (i.e., the horizontal motion due to air currents) but also the growth and decay of the organized storm with no significant success. The lifetime of individual cells within the organized storm can be 20 minutes or less. New cells frequently grow near old decaying cells, but not necessarily along the direction of motion of the old cells. As a result of this discrete propagation (i.e., growth and decay process), storm motion can appear to deviate from cellular advection. For short term predictions (e.g., 20 minutes or less), the tracking of cell motion yields accurate predictions. Longer term predictions (e.g., greater than 20 minutes) based on the tracking of cell motion are considerably less accurate. Instead, a prediction of the envelope of the organized storm is desirable.